.
According to Gen 1:4-5 and Gen 1:14-18, God keeps the timing of Days and Nights
distinctly separate, viz: Days begin at sunrise; and Nights begin at sunset; in other
words: Day is when it's light outside, and Night is when it's dark outside. It's
important to take those distinctions into consideration when calculating the
chronology of the three days and three nights predicted by Matt 12:40.
BTW: A strict chronology of "evening and morning" actually describes overnight. In
other words; it appears that God did all His work of creation in the dark. However,
if we allow "evening" to be the hours from high noon till sundown, and allow
"morning" to be the hours from sunup to high noon, then we have enough daylight
to call evening and morning a normal day.
• John 11:9-10 . . Are there not twelve hours in the day? If anyone walks in the
day, he does not stumble, because he sees the light of this world. But if anyone
walks in the night, he stumbles, because the light is not in him.
FYI: Days divided into twelve equal periods of sunlight were regulated by what's
known as temporal hours; which vary in length in accordance with the time of year.
There are times of the year at Jerusalem's latitude when this world's light consists
of less than 12 normal hours of sun, and sometimes more; but when Jesus was
here; the official number of hours was always twelve regardless.
I don't exactly know why the Jews of that era divided their days into twelve equal
periods of sunlight regardless of the seasons, but I suspect it was just a convenient
way to operate the government and conduct civil affairs; including the Temple's
activities (e.g. the daily morning and evening sacrifices)
_